Signal responsive device



Dec. 15, 1959 s.. R. ovsHlNs-KY 2,917,599

SIGNAL RESPONSIVE DEVICE Filed April 7, 1958 if ,5% 35 rig. .1..

.454,242/44 4 if j] W g7/\"" 4f j! if INVENTQR. 527427257] VSZ 'WS/aUnited States Patent C) SIGNAL RESPDNSIVE DEVICE Stanford RobertOvshinsky, Detroit,

Tann Corporation, Michigan Mich., assigner to Detroit, Mich., acorporation of This invention relates to control devices andparticularly to a circuit control device responsive to signals appliedthereto.

The device of the present invention embodies a housing enclosing achamber containing a dielectric iluid in which conducting particles aremaintained in suspension. Electrodes are provided at the ends of thehousing energized from a high potential voltage source for producing alarge difference of potential across the electrodes to accumulate andcompact the particles to form a conducting path. Such a path may beformed across a pair of contacts adjacent to one end of the body oracross the contacts adjacent to the opposite end4 thereof. When thecontacts are so bridged by the abutting particles, a circuit iscompleted thereby. Coils may be mounted at each end of the housingadjacent to or surrounding the electrodes and energized from a source ofcurrent to produce magnetic fields. Such fields will act upon theparticles when of conducting magnetizable material, and the grouping ofthe particles by the field will produce a conducting path across a pairof the contacts. The degree of conductivity of the path will depend uponthe strength of the field applied to the particles. Similarly, coils maybe mounted diagonally across corners at opposite ends of the housingwhich will complete a circuit across a diagonal path between contactslocated at opposite corners of the housing. The coils will compact theparticles along a line diagonal between a set of the contacts located atopposite corners within the housing. In this manner differentcircuitsrnay be completed under the control of current signals to thecoils which produce the magnetic fields or under the control of the highpotential voltage to the electrodes, or both, depending upon the kindand number of circuits which are to be controlled by the compacting ofthe particles. A11 electrode may be mounted in each of the four sides ofa housing, any one of which may be connected to a high potential Voltagesource for grouping and compacting the particles which are suspended in'the dielectric liquid within the interior of the housing. Contacts areassociated with each of the electrodes connected in different circuitswhich may be bridged by the particles when compacted along linesextending across opposite sides of the housing when the respectiveelectrodes thereof are energized from the voltage source or when theelectrodes of adjacent sides are energized to have opposite polaritiesfor compacting the particles diagonally across the corners between thecontacts in the adjacent sides to complete a circuit through theadjacent contacts. The housing having the electrodes in the four sidesmay have a porous body on the interior containing conductive particleswhich would not complete a path across a pair of contacts extending intothe body until a signal is applied to the electrodes. The high potentialvoltage source may be connected to the electrodes through individualswitches so that the particles may be compacted across the oppositesides or across the corners to form a conducting path or paths whichcomplete a circuit or circuits bridged thereby. The Y difference inpotential between the electrodes controls the amount of compacting, thehigher the difference the greater compacting and therefore the betterconducting path provided so that a greater amount of current may betransferred through the` circuit.

Accordingly, the main objects of the invention are: to provide a devicehaving a plurality of conducting particles suspended in a dielectricliquid which are grouped and compacted to form a conducting path acrossa pair of contacts to complete a circuit; to provide a dielectric liquidwithin the interior of the housing having conducting particles suspended.therein and rendered conductive by the application of a high potentialvoltage field or a magnetic field, or'both, thereto for grouping theparticles and forming a conducting path which bridges the contacts tocomplete a circuit thereacross; to provide a porous body within theinterior of a housing containing conducting particles which are groupedin conducting relation to complete a circuit by a change of conductivestate of said porous body by a voltage field or a magnetic field, orboth; to control the passage of current in a circuit connected to a pairof spaced contacts by grouping suspended particles to form a conductivebridge across the contacts under the influence of a voltage or magneticfield; to control the passage of current in a circuit connected to pairsof spaced contacts when compacting particles suspended in -a dielectricliquid by a Voltage or magnetic field, or both, producing conductivepaths across pairs of spaced contacts, and, in general, to provide acontrol device which is simple in construction, positive in operation,and economical of manufacture.

Other objects and features of novelty of the invention will bespecifically pointed out or will become apparent when referring, for abetter understanding of the invention, to the following descriptiontaken in conjunction with the accompanying drawing, wherein:

Figure l is a sectional view in elevation of a device embodying featuresof the present invention;

Fig. 2 is a View of structure similar to that illustrated in Fig. l,showing another form of the invention;

Fig. 3 is a View of a device similar to that illustrated in Figs. l and2, showing a still further form of the invention;

Fig. 4 is a sectional view of structure similar to that illustrated inFig. 2, showing a further form which the invention may assume, and

Fig. 5 is a view of structure similar to that illustrated in Fig. 3 inwhich conducting material is illustrated as being employed with anelement having a porous body.

The present invention embodies a device which controls the flow ofcurrent when employing a dielectric fluid containing minute particleswhich form a conducting path through the fluid when moved intoconducting relationship with each other. This may be done by employing ahigh potential field, by utilizing a magnetic eld, or by charging theparticles to cause them to respond to a given signal. In Fig. l, forexample, an insulating body 21 has a hollow interior 22 filled with adielectric liquid 23. The liquid contains a. plurality of minuteparticles 24 which in the present instance are conductive so as to forma conducting bridge between contacts when moved into contiguousrelationship to each other. A pair of contacts 25 and 26 may be employedat one end of .the body and a pair ofcontacts 27 and 28 may be employedat the opposite end thereof. When the particles 24 bridge the contacts25 and 26, a circuit is completed g and 27 and 28 to complete bothcircuits orto be dispersed and moved therefrom to interrupt both of thecircuits. Thus, by the application of voltage from a source 32 to theend electrodes 29 and 31, a desired difference of high potential voltageis provided thereacross which forms clumps of the particles adjacent tothe electrodes which bridge the adjacent contacts to make a circuit.When the voltage repels the particles at the electrodes, they move outof bridging relationship to the contacts to thereby interrupt thecircuit or circuits. When employing a relatively low voltage, theparticles will form a clump adjacent to one of the electrodes iiitherebybridge the adjacent pair of contacts to complete a circuit thereaerosswhile the circuit at the other pair ot contacts remains open. At ahigher voltage the particles will be agitated and move lengthwisebetween the ends of the body and form conducting chains tween thecontacts 26 and 27 and the clumping of the particles across the contacts25 and 28 across which a circuit will also be completed. This highervlotage could be applied at the opposite corners of the spaced ends ofthe body as to electrodes 33 and 34, which will cause the agitation ofthe particles and the accumulation of a chain or chains thereof betweenthe contacts 25 and 27 to complete a circuit diagonally across the body.A similar set of electrodes could be used at the opposite corners toproduce the accumulation of chains of the particles between thediagonally located contacts 26 and 28.

A pair of magnetic coils 35 and 36 are shown at the corners of the bodywhich when energized from a source of current produce a magnetic eldwhich moves the particles into conducting relationship between theelectrodes 26 and 28 when the particles are made of a magnetizablematerial. Similarly, the movement of the particles into conductingrelationship at one or the other or at both ends of the body across theconductors 25, 26, 27 and 23 can be controlled by magnetic elds when theparticles are made of magnetizable material. When magnetic particles areemployed, a magnetic coil 37 may be provided adjacent to one end of thebody, while a coil 33 is mounted at the opposite end thereof. It will beapparent that the energization of one of the coils will cause the ironparticles to clump or gather together adjacent to one set of contacts,and when de-energized and the opposite coil energized, the clump ofparticles will be broken up and the particles will move to the oppositeend of the body to form a conducting bridge between the other set ofcontacts. Similarly, the chain of particles formed between theelectrodes 26 and 28 when the field is produced by the coils 35 and 36may be interrupted by the presence of a difference in potential acrossthe electrodes 33 and 34 across opposite corners of the body. Thus,whenever the particles are maintained engaged to complete a circuitacross a pair of contacts, a high potential voltage may be appliedthereto to cause the particles to separate and thereby interrupt thecircuit across the contacts. Thus, it can be seen that various types ofenergy in the nature of signals may be applied to the device to make andbreak a circuit or a plurality of circuits simultaneously between theplurality of contacts 25, 26, 27 and 23 when bridged by a conductinggroup of particles.

Various types of dielectric uid may be employed in the chamber withinthe body of the device. Silicon fluid was successfully employed in whichthe frequency of movement of particles was controlled by its viscosity.For example, .65 Dow Chemical 200 fluid permitted a rapid movement ofthe particles therein. A heavier iluid, such as #50 Dow Chemical 200,will slow down the movement of the particles. The dielectric uid has theadvantage of preventing an arc from forming, and if formed, toimmediately quench the arc. It is within the purview of the invention toemploy dielectric particles having a higher degree of insulationproperties than that of the dielectric liquid which can be charged bythe applied potential and caused to collect adjacent to a current .4path to provide further assurance against the passage of a current or toquickly de-ionize an arc path if an arc has been established. Highervoltages may be employed when using the dielectric uid as it willprevent the breakdown of the medium through which the voltage ispassing. This permits the ball to receive a higher amount of chargewhich increases its speed of oscillation beyond that which would bepossible in air. This higher amount of energy imparted to the ballprovides it with a greater impact and ability to move against gravityand against other iorces opposing its movement. When the unit operatesin a vertical position, the particles may be suspended at some pointbetween the ends of the body. Thus, there is a migration of particles atcertain potentials at an associated speed, and depending upon the visecof dielectric fluid, there is a clumping of particles at a certainvoltage. There is a tremendous amount of individual particle activityeach repulsing the other in rapid movement at a higher voltage. Thiscauses the formation oi a chain of particles lengthwise of the body tocomplete a circuit between contacts 26 and 27 and/or contacts 25 and 2S.

ln Fig. 2 a device similar to that illustrated in Fig. l has a body land an internal chamber 42. A dielectric liquid 43 is contained withinthe chamber and is provided with a plurality of conducting particles 44retained in suspension therein. A pair of contacts 45 and 46 are mountedat opposite ends of lthe chamber 42 and are connected in a circuit 147.An electrode 48 is mounted at one end of the body and a similarelectrode 49 is provided at the opposite end thereof. The electrodes areconnected by a circuit 50 to a source of voltage 51 through a signalactuated device 52 which makes and breaks the circuit. Upon receiving aproper signal, the device 52 completes a circuit to the electrodes 4Sand 49 from the voltage source 51 to thereby cause a clumping of theparticles i3 between the contacts 45 and 46 to thereby complete thecircuit 47. When the signal is no longer received by the device 52, thecircuit 50 will be interrupted and the ab'utted particles 44 will bedispersed to interrupt the circuit between the contacts 45 and 46.

Referring to Fig. 3, a further form of device is illustrated, thathaving an insulating body 54 containing electrodes 55 and 56 at oppositeends and electrodes 57 and 58 transversely across the body. The chamberin the interior of the body contains a dielectric liquid 23, such asthat hereinabove referred to, containing a plurality of conductingparticles 61. The electrodes 55 and 57 are connected into a circuit 62containing a high potential voltage source 63 and controlled by adouble-pole, double-throw switch 64. The electrodes 56 and 58 areconnected by a circuit 65 to a voltage source 66 controlled by adouble-pole, double-throw switch 67. As herein illustrated, theelectrodes 55 and 56 have the same polarity, while the electrodes 57 and58 have the oppesite polarity. This will cause a repulsion of theparticles across the electrodes and the clumping of the particlesbetween the electrodes 56 and 57 and 55 and 58. T hrough the operationof the switch 64 to its second position, the electrode 57 will have theplus sign and the electrede 55 the minus sign. As a result, theparticles will bc attracted to form a clumping of the particles betweenthe electrodes 57 and 58 and between the electrodes 55 and 56. A circuit68 has a contact 69 adjacent to the electrode 56 and a contact 71adjacent to the electrode 57. A circuit l has a contact 73 adjacent tothe electrode 58 and a contact 74 adjacent to the electrode 55. When theparticles are clumped between the electrodes 55 and 5S, the circuit 72is completed across the contacts 73 and 74, and when clumped between theelectrodes 56 and 57, a circuit 68 is completed between the contacts 69and 7i. Upon reversing the vswitches 64 or 67 and the dispersion of theparticles between the electrodes 57 and 58 and 55 and 56, beth of thecircuits 72 and 68 are interrupte Thus it will. be seen that by changingthe position of the switch 64 and/or 67, the polarity of the pairs ofelectrodes shown or of any number of pairs of such electrodes will bechanged to produce the clumping or the dispersion of the particles inany part of the interior of the body to thereby complete or interruptthe associated circuits.

In Fig. 4 another control device is illustrated, that having aninsulating body 76 containing a chamber 77 having a dielectric liquid78, such as above mentioned, within the chamber containing particles 79of graphite in suspension. An lectrode 81 is mounted in the body at oneend of the chamber and an electrode 82 mounted in the body at theopposite end thereof. The electrodes are connected in a circuit 83containing a signaling device 84 from a voltage source 85 energized froma circuit 86. Contacts 87 are spaced apart across the intermediateportion of the chamber connected in a circuit 88. Contacts 89 aresimilarly spaced across the chamber 77 connected in a circuit 91. When ahigh potential voltage is applied to the electrodes 81 and 82, apressure is produced upon the collective particles to cause them tobecome sufficiently compacted to pass a current across a pair of theelectrodes 87 or 89 depending at which end of the body the compacting ofthe graphitic particles takes place. Upon an increase of voltage agreater compacting occurs through the increased pressure applied to theparticles, resulting in a better conducting path which permits a greateramount of current to be carried by the circuits 8 8 or 91. As a result,the current which is carried by the circuits 88 and 91 is modulated bythe amount of high potential voltage applied across the electrodes 81and 82.

In Fig. 5 a further form of the invention is illustrated, that whereinan insulating body 92 has a body 93'of porous` material in which aplurality of conducting particles 95 are loosely maintained. Electrodes96 and 97 are mounted in the opposite end of the body 92. An electrode98 is mounted in one side of the body diametrically opposite to anelectrode 99 in the opposite side thereof. A circuit 101 connects theelectrodes to a source of high potential voltage 102, controlled byswitches 103, 104, S and 106. Any number of sets of contacts 107 and 108may extend into the porous body 93 connected in a circuit 111 andinterrupted by the porous material of the body 93 which is relativelynonconducting. It is only when the conducting particles 94 have apotential bias applied thereacross to produce a conducting path that thecontacts 107 and v108 are conductively joined to complete the circuit111. The porous material itself will not carry current, and theparticles 95 are moved into conducting relationship by applying a highpotential voltage thereon from pairs of the electrodes 96, 97, 98 and99. This is accomplished by operating certain of the switches 103, 104,105 and 106 and causing the particles to move into conductingrelationship across a set of contacts, such as contacts 107 and 108, tocomplete the circuit 111. In this instance the circuit could have beencompleted by closing the switches 104 and 106 to provide a highpotential voltage across the electrodes 99 and 98. A conducting pathsimilarly would be provided if the high potential voltage was appliedbetween the electrodes 96 and 97 by the closing of the switches 103 and105 to group the particles 95 sufficiently to pass current across a setof contacts, such as contacts 107 and 108. It is very obvious that byincreasing or decreasing the high potential voltage, the degree ofconductivity through the path of the resulting grouped particles 95 canbe changed. It is also obvious that by applying the high potentialvoltage to pairs of the electrodes independently or simultaneously, adegree of concentration of the conductive particles may be controlledwithin the porous body 93 to increase the conducting path between thecontacts 107 and 108 to thereby pass a still greater amount of currentthrough the circuit 111. Thus the conducting particles within -theporous body 93 will produce substantially no conducting path until apotential bias is applied across pairs of the electrodes 96, 97, 98 and99. This occurs through the operation of the associated switch 103, 104,and 106, the degree of conductivity depending upon the number ofswitches closed and the increase in the difference of potential betweenthe electrodes. Similarly, the particles or chargeable means may havegood dielectric properties which, when forced in the pores of the body93 by the potential field across the electrodes, will increase thedielectric properties of the body and provide increased opposition tothe passage of a current thereacross.

When the word ball is employed throughout the specication and claims, itis to be understood that a true spherical element is not necessarilyreferred to, since the element may be of any shape and may be in somein-f stances a plurality of sizable elements or a greater numof smallelements in the nature of chargeable particles which may be compacted toproduce a conductive path. Thus, the chargeable means, whether a sphereor an irregular element or elements, or those which have been previouslycharged, will be affected by the charge applied by the difference ofpotential across the electrodes to change the conductivity across a pairof contacts, as-

herein disclosed. It is also to be understood that the elements andparticles can be magnetic, conductive or nonconductive since they willbe affected by the ditference of potential across the electrodes to bemoved in a manner' to change the conductivity of a path, as hereinabovedescribed. This change of state of the variable medium of the devicewill change the degree of conductivity of a` path to interrupt orcomplete a circuit, as the case may be. Thus, it will be noted that theparticles herein employed can be conducting or nonconducting or theconductivity can be changed by a change in the number of particlesengaged or the amount of pressure applied thereto by the voltageor'magnetic field. For example, carbon particles may have a forceapplied thereto by a nonm-echanical field which will result in asubstantial increase in conductivity to pass an increased amount ofcurrent therethrough. The particles may be of uniform size and shape ormay be entirely nonuniform, but such particles must be of a size whichmay be readily charged and moved into compacting relationship to form aconducting path when the particles are of conducting material or adielectric path when they are of insulating material.

What is claimed:

1. In a control device, a housing having an interior chamber, adielectric liquid within the chamber, conducting particles within thedielectric liquid, and a pair 0f electrodes in said housing in spacedrelation to each other energizable from a voltage source for producingan electrostatic eld and charges which compact the particles to form aconducting path thereof.

2. In a control device, a housing having an interior chamber, adielectric liquid within the chamber, conducting particles within thedielectric liquid, a pair of electrodes in said housing in spacedrelation to each other I energizable from a voltage source for producingan electrostatic field and charges which compact the particles to form aconducting path thereof, and a pair of contacts energizable from avoltage source for producing an electrostatic iield and charges whichcompact the particles to form a conducting path thereof, a pair ofcontacts adjacent to one of said electrodes which are bridged by v theconducting path formed by said particles, and a second set of contactsadjacent to the other of said electrodes which are bridged by theconducting path when the particles are compacted adjacent to said secondelectrodes.

4. In a control device, a housing having an interior chamber, adielectric liquid within the chamber, conducting particles within thedielectric liquid, a pair of electrodes in said housing in spacedrelation to each other energizable from a voltage source for producingan electrostatic field and charges which compact the particles to form aconducting path thereof, a pair of contacts adjacent to one of saidelectrodes which are bridged by the conducting path formed by saidparticles, a second set of contacts adjacent to the other of saidelectrodes which are bridged by the conducting path when the particlesare compacted adjacent to said second electrodes, and a coil adjacent toeach of said electrodes energized from a source of current to produce amagnetic field which compacts the particles and moves them intoconducting relationship across the pair of contacts adjacent thereto.

5. In a control device, a housing having an interior chamber, adielectric liquid within the chamber, conducting particles within thedielectric liquid, a pair of electrodes in said housing in spacedrelation to each other energizable from a voltage source for producingan electrostatic field and charges which compact the particles to form aconducting path thereof, a pair of contacts adjacent to one of saidelectrodes which are bridged by the conducting path formed by saidparticles, a second set of contacts adjacent to the other of saidelectrodes which are bridged by the conducting path when the particlesare compacted adjacent to said second electrodes, a coil adjacent toeach of said electrodes energized from a source of current to produce amagnetic field which compacts the particles and moves them intoconducting relationship across the pair of contacts adjacent thereto,and a coil at diagonal corners of said housing energized from a sourceof current to produce a magnetic field diagonally between contacts atthe opposite corners of the housing to compact the particles and form aconducting path diagonally between said contacts.

6. In a control device, a housing having an interior chamber, adielectric liquid within the chamber, conducting particles within thedielectric liquid, a pair of electrodes in said housing in spacedrelation to each other energizable from a voltage source for producingan electrostatic field and charges which compact the particles to form aconducting path thereof, a pair of contacts adjacent to one of saidelectrodes which are bridged by the conducting path formed by saidparticles, a second set of contacts adjacent to the other of saidelectrodes which are bridged by the conducting path when the particlesare compacted adjacent to said second electrodes, a coil adjacent toeach of said electrodes energized from a source of current to produce amagnetic field which compacts the particles and moves them intoconducting relationship across the pair of contacts adjacent thereto, acoil at diagonal corners of said housing energized from a source ofcurrent to produce a magnetic field diagonally between contacts at theopposite corners of the housing to compact the particles and form aconducting path diagonally between said contacts, and electrodes appliedto opposite corners of the housing energizable from a voltage source forproducing a conducting path by compacting the particles diagonallybetween contacts at opposite corners of the housing.

7. In a control device, a housing having an interior chamber, adielectric liquid within the chamber, conducting particles Within thedielectric liquid, a pair of electrodes in said housing in spacedrelation to each other energizable from a voltage source for producingan electrostatic field and charges which compact the particles to form aconducting path thereof, a pair of contacts adjacent to one of saidelectrodes which are bridged by the conducting path formed by saidparticles, a second set of contacts adjacent to the other of saidelectrodes which are bridged by the conducting path when the particlesare compacted adjacent to said second electrodes, a coil adjacent toeach of said electrodes energized from a source of current to produce amagnetic eld which compacts the particles and moves them into conductingrelationship across the pair of contacts adjacent thereto, andelectrodes applied to opposite corners of the housing energizable from avoltage source for producing a conducting path by compacting theparticles diagonally between contacts at opposite corners of thehousing.

8. In a control device, a housing having a hollow interior, a dielectricfluid within said interior, pairs of contacts within said housing,spaced electrodes in said housing for producing an electrostatic fieldwhen energized, spaced coils on said housing energized by a current toproduce magnetic fields across pairs of said contacts, conductingparticles of magnetizable material suspended in said uid and compactedby said fields to form conducting paths across the associated pairs ofcontacts, and additional coils at diagonal corners of the housing forcompacting the particles and producing a conducting path betweencontacts at diagonal corners of the housmg.

9. In a control device, a housing having a hollow interior, an electrodein each of the four sides of the housing energizable from a source ofvoltage to produce electrostatic fields, contacts within the interior ofthe device adjacent to each of said electrodes, conductors connected toeach of said contacts to form circuits, a dielectric liquid within theinterior of the housing, conducting particles suspended in said liquid,said particles being compacted to form a conducting path between a pairof contacts when the associated pair of electrodes are energized from avoltage source to have opposite polarity to charge and compact saidparticles and complete a circuit across opposite sides of the housingand/ or diagonally across the corners thereof depending upon whichelectrodes are energized.

l0. In a control device, a housing, electrodes in each end of thehousing, pairs of contacts extending across opposite sides of thehousing, dielectric fiuid within said housing, conducting particlessuspended in said dielectric liuid, said particles being compacted intoa conducting path which bridges the contacts to complete a circuit whena voltage is applied to said electrodes for producing an electrostaticfield, and a signal responsive switch in the voltage circuit forcompleting a circuit to the electrodes when a proper signal is received.

ll. ln a control device, a housing, a porous body within said housing,conducting particles in said porous body, electrodes in the walls ofsaid housing, contacts adjacent to the paths between said electrodes,and switch means for connecting a voltage source to any number of saidelectrodes to apply an opposite polarity to at least a pair of saidterminals for producing an electrostatic field which compacts theparticles and produces a conducting path which bridges a pair ofcontacts to complete a circuit.

l2. In a control device, a housing having a hollow interior, spacedcontacts of a circuit within said housing, a dielectric fluid within theinterior, graphite suspended within said fiuid, and electrodes in saidhousing to which a voltage source is applied for producing anelectrostatic field which compacts the graphite to thereby formconducting paths across a pair of contacts.

13. In a control device, a housing having a hollow interior, spacedcontacts of a circuit within said housing, a dielectric fluid within theinterior, graphite suspended within said fluid, and electrodes in saidhousing to which a voltage source is applied for producing anelectrostatic iield which compacts the graphite to thereby formconducting paths across a pair of contacts, the conductivity of saidpaths being increased by an increase in the voltage applied to the pairof terminals.

14. In a control device, a housing having ya hollow in- 9 terior, spacedcontacts of a circuit within said housing, a dielectric uid within theinterior, chargeable means suspended within said uid, and electrodes insaid housing to which a voltage source is applied for producing anelectrostatic field which charges said means to thereby form aconducting path across said contacts.

15. In a control device, a housing, a porous body Within said housing ofdielectric material, particles adjacent to said body having greaterdielectric properties, electrodes in the walls of said housing, andmeans providing a diierence of potential across said electrodes forcharging the dielectric particles and causing them to move into thepores of said body to increase the dielectric strength thereof.

16. In a control device, `a housing having a hollow interior, spacedcontacts of a circuit within said housing, a mediumv within saidinterior in which a change of state may occur, and electrode means insaid housing to which a voltage source is applied for producing anelectrostatic 10 field across said medium to effect a change therein andin the conductivity of the path across said contacts.

17. In a control device, a housing having a hollow interior, spacedcontacts of a circuit within said housing, a medium Within said interiorin which a change of state may occur, and electrodes in said housing towhich a voltage source is applied for producing an electrostatic fieldacross said medium to effect a change therein and in the conductivity ofthe path across said contacts, the greater the difference in potentialbetween said electrodes the greater the change in conductivity producedin said medium.

References Cited in the le of this patent UNITED STATES PATENTS

